It is well known in the art of double-lock-stitch sewing machines that an upper thread is carried by a needle through a stitch plate to form therebelow a bight which is looped by a rotary hook or gripper assembly about a bobbin thread to form a lock stitch.
The gripper assembly includes a main hook or point for engaging the upper-thread loop at the moment of its formation and passing it around a substantially stationary bobbin, whereupon the loop is taken up by a counter hook on the gripper assembly in order to prevent its moving about and possible re-engagement by the main hook.
The counter gripper or counter point has a generally frictionless lower edge facilitating acceptance of the loop from the main hook and guiding the loop as it moves prior to the formation of a subsequent stitch. The lower edge of the counter hook is rendered nearly friction-free by adapting the edge's angle of inclination to the movement of thread-control lever of the particular machine.
The above-described double-lock-stitch sewing machine performs excellently under usual circumstances. However, in the case of ornamental stitching, which generally utilizes heavier thread and greater stitch lengths, such a machine will produce a seam which bunches the material.